The present invention generally relates to electrostatic discharge protection (ESD) systems and more particularly to a system and a method for protecting an electrically-inactive component of a microsystem from an ESD event.
Electrostatic discharge (ESD) events are potentially serious occurrences that can cause major damage to microsystems such as intergrated circuits (ICs) and microelectromechanical systems (MEMS or, more simply, micromachines). A typical ESD event is usually a high voltage occurrence and can easily damage or destroy a microsystem, which is designed to operate at small voltages.
Microsystems typically contain both electrically-active (or electrical) components (such as, for example, resistors and capacitors) and electrically-inactive components (such as cantilevered beams, gears and thin-film layers) that have a primarily non-electrical or mechanical function. Microsystems are vulnerable to ESD events because of their small size and an ESD event can easily damage or destroy the components contained within the microsystem. Further, damage can occur not only to the electrical components of the microsystem, but also to the electrically-inactive components of the microsystem.
Although many microsystems contain ESD protection systems, current ESD protection schemes are designed to protect only the electrical components of the microsystem. Hence, the electrically-inactive components are generally left unprotected from potentially damaging ESD events. This is a problem because, even if the electrical components have ESD protection, an ESD event still can cause damage to the electrical components of the microsystem, especially if the electrically-inactive component is in close proximity to the electrical component. Therefore, there exists a need for an ESD protection system that provides protection from ESD events for not only electrical components of a microsystem, but also the electrically-inactive components.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention is embodied in a novel system and method for protecting a microsystem from electrostatic discharge (ESD) by protecting an electrically-inactive component of the microsystem. By providing ESD protection to the electrically-inactive component, a more complete and efficient ESD protection system is achieved that also provides additional protection for any sensitive electrical components of the microsystem. The present invention may be used in microsystems (such as integrated circuits and micromachines) that contain electrically-inactive components. Electrically-inactive components include those components of the microsystem that have no electrical function and those structures (for example gears, thin-film layers and cantilevered beams) that have a primarily mechanical purpose.
The present invention is provides highly effective and efficient ESD protection to Microsystems having electrically-inactive components. In particular, by providing ESD protection to the electrically-inactive components of the microsystem as well as the electrical components the present invention greatly reduces the sensitivity of a microsystem to ESD events. Moreover, the present invention may be implemented easily within a microsystem using existing structure and circuitry or by microfabrication techniques that are well-known in the art.
The system of the present invention includes an ESD protection system that is positioned to direct an ESD event away from an electrically-inactive component of a microsystem. The ESD protection system of the present invention is designed either to reduce the damaging effects of an ESD event or prevent the ESD event from occurring. The present invention includes several embodiments of the ESD protection system that are used to accomplish these purposes.
In particular, one embodiment the ESD protection system provides an electrically floating large conductive area for disipatiion of an ESD event. This large conductive area, which is capacitively coupled to an electrically-inactive component, reduces the susceptibility of the electrically-inactive component by providing a storage area for the ESD event. In another embodiment, the large conductive area and the electrically-inactive component are kept at the same potential or ground, thereby greatly reducing the occurrence of an ESD event. Furthermore, in order to provide ESD protection during a manufacturing process, the embodiment may include a severable link (such as a fuse) so that the electrically-inactive component and the large conductive area are kept at the same potential for a certain period of time before the connection between the large conductive area and the potential is severed. In this way, the ESD protection system greatly reduces the occurrence of an ESD event during the manufacturing process without affecting the normal operation of the microsystem.
Another embodiment of the present invention includes an ESD protection system that provides a preferred breakdown location for an ESD event at a location away from any electrically-inactive components. In this way, even if all other ESD protection systems fail the resulting damage to the microsystem will be in a location that does not affect the microsystem operation. Other embodiments of the present invention include various ESD protection system designs that divide the large conductive area within the microsystem into various planes. The charge from an ESD event is store in these various planes thereby avoiding the creation of a high charge area in a plane that could damage the plane. Furthermore, a shunt bar is introduced in several designs to provide an ESD event with a preferred path to flow, this preferred path being away from the electrically-inactive component. The present invention also includes a method of protecting a microsystem having an electrically-inactive component using the aforementioned systems.
Other aspects and advantages of the present invention as well as a more complete understanding thereof will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Moreover, it is intended that the scope of the invention be limited by the claims and not by the preceding summary or the following detailed description.